From: Colin Bartlett <colinb2r@...>
Date: 2010-07-21T00:32:37+09:00
Subject: Re: Count occurences of vars in array

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On Tue, Jul 20, 2010 at 2:47 PM, Vitaliy Yanchuk <fuksito@gmail.com> wrote:

> ... Would be grateful if someone can tell, how can I do shortly (mb with
> one
> method) from such example array
>   ["a", "b", "a", "c", "c", "b", "b"]
> The result: a => 2, b => 3, c => 2. So, to count number of occurances.


def owtdi( ary ); h = Hash.new(0); ary.each {|e| h[e] += 1}; h; end
def owtdi2( ary ); ary.inject(Hash.new(0)) {|h,e| h[e]+= 1; h}; end

def tmtowtdi( ary )
  ary = ary.sort; test_v = ! ary[0]; cary = []; kt = nil
  ary.each do |vv|
    if vv != test_v then
      cary << [test_v, kt]  if kt
      test_v = vv; kt = 0
    end
    kt += 1
  end
  cary << [test_v, kt]  if kt
  cary
end

rr = ["a", "b", "a", "c", "c", "b", "b"]
p owtdi( rr ), owtdi2( rr ), tmtowtdi( rr )
kt = 100_000
require "benchmark"
ow = ow2 = tmtow = nil
Benchmark.bmbm do|b|
  b.report("owtdi") { kt.times { ow = owtdi( rr ) } }
  b.report("tmtowtdi") { kt.times { tmtow = tmtowtdi( rr ) } }
end
puts; p ow, tmtow
__END__
{"a"=>2, "b"=>3, "c"=>2}
[["a", 2], ["b", 3], ["c", 2]]

               user     system      total        real
ruby 1.8.6 (2007-09-24 patchlevel 111) [i386-mswin32]
owtdi      3.572000   0.016000   3.588000 (  4.422000)
tmtowtdi   4.883000   0.031000   4.914000 (  5.819000)

ruby 1.9.1p243 (2009-07-16 revision 24175) [i386-mingw32]
owtdi      2.558000   0.047000   2.605000 (  3.243000)
tmtowtdi   1.545000   0.015000   1.560000 (  1.943000)
  another 1.9.1 run: owtdi user = 2.293 and tmtowtdi user = 1.810;

jruby 1.5.0.RC1 (ruby 1.8.7 patchlevel 249) (2010-04-14 0b08bc7)
 (Java HotSpot(TM) Client VM 1.6.0_14) [x86-java]
owtdi      1.980000   0.000000   1.980000 (  1.979000)
tmtowtdi   1.523000   0.000000   1.523000 (  1.522000)
I ought to point out that in a subsequent JRuby run
 owtdi user = 1.625 and tmtowtdi user = 1.809,
 and in another run owtdi user = 2.118 and tmtowtdi user = 1.987,
so quite variable! But there was quite a lot of apparently random and
purposeless disk i/o going on while the benchmarks were running. (Thank you,
Windows Vista!) So I would place even less reliance than usual on these
benchmarks. But using inject does seem significantly slower, especially so
using 1.8.6.

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